Currently the documentation on llvm.org is built using Doxygen 1.7.5.1 which was released about 5 years ago and lacks a bunch of features, notably markdown support. Could you (or someone else) upgrade Doxygen used to generate docs on llvm.org to at least version 1.8.6 (ideally, to the latest available version - 1.8.11).
Thank you for updating doxygen, Tanya! Now I see the pages generated by the new doxygen, however, the clang-tools-extra doc page seems to be built from incorrect sources (it’s titled “My Project” and doesn’t contain anything related to clang-tools-extra). When I’m building doxygen-clang-tools locally (with doxygen 1.8.6, but I don’t think this should make much difference), it seems to work fine (see the attached screenshot of my locally-generated doxygen documentation).